1. Field of the Invention
The present invention relates to tooling for machining operations and, more particularly, relates to a toolholder assembly that precisely locates a toolholder at a selected location within a tool support member during a machining operation.
2. Description of Related Art
Minimizing the down time of a machine tool in a production environment is critical to the success of a machining facility. Historically, one major contribution to such down time was the time needed to change damaged or worn out cutting tools used by the machine tool. A cutting tool is held by a toolholder, which is typically mounted within a tool support member secured to a machine tool. When the cutting tool must be replaced, the entire toolholder with the cutting tool attached thereto is removed from the support member.
A number of couplings are designed to permit quick connecting and disconnecting of the toolholder to and from the tool support member to expedite the tool changing process. One such device is described in U.S. Pat. No. 4,723,877 entitled “Toolholder.” This patent is co-owned by the Assignee of the present application and is hereby incorporated by reference in its entirety. The toolholder assembly described in that patent utilizes two locking balls which are urged radially outwardly within a tool support member to engage apertures on the shank of a toolholder. While this arrangement is efficient and permits a toolholder to be removed or secured to a tool support member in a short amount of time, the associated assembly uses apertures in the ball canister and the shank of the toolholder having a diameter slightly larger than the diameter of the locking balls. As a result, the balls are free to roll slightly along the sides of the apertures and lock the toolholder in place in slightly different radial positions. In the worst case, the ball could locate up to 0.002″ on either side of the center in both the canister and the toolholder shank resulting in a maximum displacement of 0.004″ of the toolholder from the specified position. The displacement directly affects the center height location of the insert edges on the cutting tool. Center height accuracy is what controls the diameters of the workpiece in the machine tool, often a critical dimension.